Building and maintaining urban WiFi access point (AP) databases can benefit positioning and navigation applications. In conventional approaches for building and maintaining urban WiFi AP databases, a crowdsourcing server would periodically send instructions to all crowdsourcing mobile clients instructing them how to collect crowdsourcing data. One issue with this approach is that such instructions may unnecessarily flood the network and waste valuable bandwidth of the mobile clients. However, without such periodic crowdsourcing instructions sent from the crowdsourcing server to the mobile clients, the crowdsourcing server may not get sufficient data from the mobile clients, which in turn may lead to poor quality of the WiFi AP database. In addition, the mobile clients may send excessive redundant data to flood the server, which not only may waste the mobile clients' valuable bandwidth and data storage space, it may also cause the crowdsourcing server to consume additional effort to search and extract useful data from the mobile clients.
Therefore, there is a need for methods and systems that can address the above issues of conventional solutions.